Telephone system



Original Filed April 29, 1926 Patented Mar. 26, 1929.

UNITED STATES PATENT OFFICE.

BERT A. WALLACE, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWITCHBOARED AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM.

Application filed April 29, 1926, Serial No. 105,339. Renewed July 28, 1928.

My invention relates to telephone systems, and more particularly to that system wherein manually operated cord or link circuits are employed for interconnecting common battery telephone lines, or for interconnecting magneto lines, or for interconnecting common battery telephone lines and magneto lines.

A feature of my invention is the provision of a meter circuit associated with the cord circuit which is adapted to automatically register answered calls when the answering end of the cord is connected to a common battery calling line.

Another feature of my invention is the provision of means in the meter circuit which prevents the meter from registering should the operator attempt to register false calls by inserting an answering plug of a cord pair into the jack of a noncalling line.

Another feature of my invention is the provision of means whereby the meter relay fails to operate should a second operator attempt to answer a call from a calling common battery subscribers line subsequent to the connection of the first. operator thus preventing the registration of an answered call.

The above features, as well as others not specifically pointed out, will be more fully hereinafter described.

For a more complete and better understanding of my invention, reference may be had to the accompanying drawing.

Referring now in general to the drawing, I show a common battery calling substation A, and a common battery called substation B terminating respectively at the exchange in line circuits L and L. The line circuits L and L at the exchange comprise, respectively, the usual line relays LR and LR, cut-oil relays CO and CO, multiple jacks J and J, and the multiple line lamp signals S and C. The jacks of the line are distributed among different operators positions, and there is a line signal for each jack at the different operators positions at which the subscribers line terminates so that when a call is initiated over the line, the line signal at the different positions is lighted, and one of a plurality of operators may seize the call to the exclusion of the other operators.

A local battery or magneto calling substation 1) and a local battery or magneto called substation E are also shown terminating, respective y, at the exchange in line circuits L and L The line circuits L and L comprise, respectively, jacks LJ and LJ, and line drop signals DS and DS'. The signals DS and US are adapted to operate respectively when the subscribers at substations D and E initiate a call, to indicate to the operator at the exchange that a call has been initiated and that her services are desired.

The cord or link circuit C of my invention for interconnecting any two of the substations A B, D and E, as calling and called lines, is provided with an answering plug AP and a calling plug CP, the said answering plug AP and calling plug CP being operatively connected by the heavily marked conductors having the repeating coil RC and condensers K and K interposed. The answering end of the cord has a sleeve relay SR which energizes when the plug AP is inserted into a jack J, provided, however, that the plug AP or CP of another cord is not already engaging a jack J. as will be pointed out more clearly in the ensuing specification. Relay SR will not energize when the plug AP is inserted into a jack LJ of a magneto line, due to the fact that the sleeve contact of jack LJ is free from ground. An answering supervisory relay AR is provided for controlling the operation of an answering supervisory signal AS. An operat'ors listening key LK is provided for connecting the operators telephone set U to the cord circuit C, and an operators disconnect relay ODR is provided for preventing the operator from connecting her telephone set 0 to the cord C under certain conditions, to provide secret service between subscribers lines, under certain conditions, as will be pointed out later. A relay RR is provided which is bridged across the talking conductors of the cord C, and is operable to control the operation of the operators disconnect relay ODR, and also to be controlled over a magneto telephone line to effect the operation of the supervisory signal AS to signal for a disconnection and also to signal for a recall, as will be later pointed out more in detail. A ring back key RB and a generator HG are provided for applying ringing current to the calling subscribers line to signal him when the called for subscriber has answered, in case the calling subscriber replaces his receiver upon the switchhook after informing the operator of his Wants.

A meter relay MR is also associated with the answering end of the cord circuit C and is energized when the relay SR is energized, and this energization of the relay MR takes place only when the answering plug AP is connected with a calling common battery line and when the relays SR and AR are energized as will be more clearly pointed out in the ensuing specification. The meter relay R upon energization closes a locking circuit l or itself and places the meter magnet MM which is common to a group of cords in condition to be energized when the operator disconnects the answering plug AP from the calling common battery line at the termination of conversation to operate the meter M to register an answered connnon battery call.

The calling end of the cord C is provided with a sleeve relay SR which energizes when the calling plug CP is inserted into one of the multiple jacks J provided a plug AP 01' CP of another cord circuit is not already engaging one of the jacks J. The relay SR will not operate when the plug CP is inserted into a jack LJ of a magneto line, as the sleeve of the jack LJ is free from ground. A calling supervisory relay CR is provided for controlling the operation of the supervisory signal CL. A relay RR is provided for also controlling the operation of the operators disconnect relay ()DR, and also for effecting operation of the supervisory signal CL, when the plug CP is connected to a jack of a magneto line to indicate a disconnection and to also indicate a recall, which Will be fully described later.

A ringing control relay RCR is provided, which energizes when the operator depresses fully the ringing key RK, to bring about the energization of an interrupter relay IR, and to also connect an interrupter device I in circuit with the lower winding of the interrupter relay, whereby said relay IR is caused to be ii'itermittcntly operated to connect ringing current to the called subscribers line from one of the ringing frequency generators (ii, (1", (1 and U". The signal CL lights as soon as the calling plug (P is inserted into the jack J, and remains lighted until the operator depresses the ringing kcy RR: the burning lamp CL thus serving at this time as a signal to notify the operator that ringing current has not been connected to the called line. The lamp (L also serves to notify the operator when the called subscriber has replaced his receiver upon its switchhook.

hen the plug CP is inserted into a jack LJ, relay SR fails to energize, and in this case ringing current will only be applied to the called line so long as the ringing key RK is in its fully depressed position, as there will be no locking circuit provided for maintaining the ringing control relay RCR energized to close a circuit for relay lR, when the key RK is not in its fully depressed position. In this instance, the operator will depress fully key RK each time ringing current is applied to the called line terminating in jack lid.

Referring now more in detail to the opera tion of my invention, I will first describe the operation of my cord in interconnecting common battery subscribers-i telephone lines. Assuming that the subscriber at substation A desires to converse with the subscriber at substation B, he will remove his receiver from its switchhook, thus closing a circuit for the line relay LR, traced trom battery, through the windin of said relay LR, normal contact 1 of cut-oll relay Ct), line limb 2, the now alternate closed switchhoolt contacts of substation A, line limb 3, and to ground through normal contact 4 of relay CO. Relay LR energizes over this circuit and closes its inirn'ially open contact 5, thereby closing a circuit tor the line lamps S, traced from badcry, through said lamps S, the now closed contact 5 of relay LR to ground. The lamps S will be lighted over this circuit at a plurality of operators positions. Assuming that the operator at cord circuit C is the first one to answer the call, the insertion of the answering plug AP into the jack J of the calling line establishes a series energizing circuit for the cut-oil relay C0 of the line circuit L, and the sleeve relay SR, the circuit being traced from battery, through the low resistance winding 6 and high resistance winding 7 of said relay SR, conductor 8, sleeve contacts of plug AP and jack J to ground through. the winding of cut-oil relay CH. The closure of alternate contact 5) of relay SR shunts out the high resistance winding T and closes a low resistance circuit for relay SR, traced from battery through the low resistance winding (3 and alternate contact 9 of relay SR, and over the previously traced circuit. The cutoll relay CO in the line circuit li crgizcd in series with relay SR over the firs cir uit traced and will be maintained energized over the last traced circuit so long as the plug Al remains in the answering jack .l, thereby taking line relay Lil from under the c ntrol oi" the subscriber at :--ob: tation A. Relay SR upon cncr; yizing closes a circuit for the answering supervisory relay All. traced from battery through the lower winding of said relay AR, alternate contact it) of relay SR, winding c of rcpraiing coil RC, normal contact ll of key RB, ring contacts of plug AP and jack J, through the alternate ('ltisttl switchhook contacts oi substation A. tip contacts of jack J and plug Al, normal contact iii of key RP, winding (z of repeat ing coil RC, alternate contact 13 of relay SR, to ground through the upper winding of relay AR. Relay AR energizing opens its Ill) normally closed contact ll to prevent the premature lighting of the supervisory lamp AS and to remove the shunt around the meter relay Mll.

The relays SR and AR having energized, an energizing circuit for the meter relay MR is closed traced from battery through the answering supervisory lamp AS, alternate contact 60 of relay SR conductors lt)l and 102, normal contact 1.03 of relay MR, through the winding of relay hilt, conductor 104, to gound a alternate Contact too of relay SR. The meter relay MB is energized over this circuit and the closing of its make before break contact 105 closes a locking circuit for itself tr; ced from i atte y, its make before break contact 1'13 through the winding of relay MR to ground at alternate contact 100 of relay SR. The closing of alternate 001L210; 106 of the meter relay MR places the meter magnet MM in coadition to be energized to operate the meter M at the proper time will be lolly hercinatiindescribed.

The ope 'ato' at cord circuit (1 having inserted the plug AP into the multiple jack J, will operate the listening key Lli to connect her telephone set to the cord circuit C, and will then inquire the wants of the ailing subscriber at substation A. The operators set U is connected to the cord C over the following circuit, point of the tip conductor of said cord, conductor 16 alternate contact 17 of listening key LK, normal contact 18 of relay OUR, receiver of operatoi"s set 0, normal contact l9 of relay ODR, alternate contact 20 of the listening key LK, conductor 21, to p 22 of the ring conductor of cord Q.

Should another operator attempt to answer this same call initiated trom substation A, subsequently to the insertion of the plug AP of cord circuit C into the answering jack J, the said other operator will be pre' vented from connecting her telephone set in circuit viih the calling subscribcad. line even though she does operate her listening key. Thus secret service is provided he: veen the operator at cord and the sidiscribcr at substation A. whieh'is eil'ectcd in his ma ner: The radar sR ot the cord a t 1-(f( 11tl operator's position w ll not ere ize Ill this instance, due to the shunt place: about the high resistance 1 7 ol' re ay SR ot' the second operatofls cord c rcuit C by the low resistance circuit of the relay ll of the tirst operatofis cord, and this low resistance circuit will sh rat the lot: and high resistance windings of the relay SR ot the second operators cord circuit to render the same inoperative as long as the plug A1 of the co 'd C remains in the jack J. The relay SR ot' the second cord circuit tailing to energize its alternate contacts and lot remain open and therefore no energizing circuit is (stablishcd to the meter relay MR so that the meter relay MR is not affected when a second operator attempts to answer the same all subsequent to the insertion of an answering plug by the first operator. The relay SR of the second ope 'ators cord circuit failing to energize, a circuit will be closed -r the relay RR of the second operator-s cord circuit, traced from the battery potential on the ring contact ot the multiple jack,

which is in multiple circuit with the a iswering jack J of the calling line, ring contact of the answering plug of the second opcators cord circuit, normal contact 11 of key RB, ring conductor and winding 0 oi the re 'ieating coil RC of the second cord circuit, winding of relay RR, normal contact 13 of y SR, ot' the second cord, wind ng a of the repeating coil RC, tip conductor, normal contact 12 of key RB and tip contact of the answering plug of the said second ope 'ators cord circuit, and to ground at the tip contact ot' the said multiple jack which is in multiple circuit with the answering jack J oi" the calling line. Relay RR ot the second ooerators cord circuit energizing over this circuit will close its alternate contacts, which will provide an energizing circuit for the second operators disconnect relay ODE associated with said second operators cord circuit, when the second operator operates her listening key to connect her telephone set in c rcuit to permit her to converse vith the c f sibscriber at substation A, the circuit tor said relay ODE of the second cord circuit being traced from battery through the winding of rela ODR, alternate conof listening key LK, conductors 2 t tact 2o tilt 25 to ground through the alternate contact of relay RR of the said second operetors cord c rcuit. Relay ()DR 0' the sec ond operato1"s cord circuit energizing over the above traced circuit will open its nor mally closed contacts 18 and 19, thereby disconnecting the second operatofls telephone set from her cord circuit connected to the *alling subscriber s line, which will prevent the second operator from conversing with the :alling subscriber at substation A. The second operator failing to receive a response upon inquirin the wants of the calling su scribcr, will low that the call has been seized by another operator. and will disconnect her cord circuit from the multiple in ot' the callii line, whereupon the said rt lays Bit and ()Dll of the second operatons cord circuit will restore to normal.

' from the foregoing described operamo em the frequency generator G, alternate closed contact 52 and normal contact 53 of the ringing key RK, conductor 54, alternate contact 49 of the interrupter relay IR, tip contacts of plug CP and jack J, through the call bell at substation B, ring contacts of 12101: J, and plug GP, to ground through alternate contact 48 of relay IR. A revertive ringing tone is also communicated to the calling subscriber to apprise him of the fact that the called for subscriber is being signaled, the circuit for this revertive ringing tone being from ground through the generator G conductor 55, alternate contact 56 of relay IR, winding 1) of the repeating coil RC, alternate contact 50 of relay SR to ground through the upper winding of relay Ch, whereupon the said revertive ringing tone will be induced into the wind mg a of the repeating coil RC and then transmitted through the calling substation A. Should the subscriber at the substation A replace his receiver upon its switchhook before the called-for subscriber at substation B removes his receiver in response to his call bell, the further application of ringing current to the called line will be automatically discontinued, due to the fact that the supervisory relay AR which is controlled by the calling subscriber at substation A will deenergize when the calling subscriber replaces his receiver, and relay AR, restoring to normal, opens its alternate contact 36, thereby opening the locking circuit of relay RCR to cause the same to restore, which in restoring opens the circuit through the lower winding of the interrupter relay IR whereupon the relay IR immediately restores to its normal position to prevent the further application of ringing current to the called line. Assuming, however, that the calling subscriber at A does not replace his receiver before the called-for subscriber responds, after the removal of the receiver at substation l), and when relay lit is in its dccnergized position, as will be the case during a non-ringing period, a circuit will be closed for the calling supervisory relay (1%. traced from battery, through the lower winding of the relay CR, alternate contact 47 of relay SR, winding (Z of the repeating coil RC, normal contact 48 of relay IR, ring contacts of plug (DP and jack J, through the now closed alternate switchhook contacts of the substation ll, tip contacts of jack J and plug (1 normal contact 49 of relay IR, winding 0 of repeating coil RC, alternate contact 50 of relay SR, to ground through the upper winding of relay CR. Ielay CR will energize over this circuit and will open its normally closed contact 34, thereby opening the locking circuit of the ringing control relay RCR, whereupon said relay RCR will restore, as pointed out above, to prevent another energization of relay IR, whereby further application of ringing current to the called subscribers line is prevented.

The subscribers at substations A and B are now in conversational circuit, which may be traced over the heavily marked conductors. Should the operator at cord circuit C attempt to listen in on the conversation by operating her listening key LK, she is prevented from doing so by the operation of the relay ODR, which will energize to open its normally closed contacts 18 and 19. The circuit for said relay ODR may be traced from battery, through the winding of the relay ODR, alternate contact 23 of the listening key LK, conductor 24, alternate contact 58 of relay CR, conductor 59, alternate contact 60 of listening key LK, alternate contact 14 of relay AR to ground. Thus, it is clear that the operator cannot connect her telephone set in circuit so as to listen in on the conversation between the subscribers at substations A and B. In case the subscriber at substation A replaces his receiver upon its switchhook, supervisory relay AR will restore and open its alternate contact 14, thereby opening the circuit of relay ODR at alternate contact 14. Should the operator now operate her listening key LK, her telephone set 0 will be connected to the cord C, which will enable the operator to communicate with the subscriber at substation B, provided said subscriber has not replaced his receiver upon its switchhook. In case the subscriber at substation replaces his receiver upon its switchhook, supervisory relay CR will restore and open its alternate contact 34, thereby opening the circuit of the relay ()DR. The operator may now operate her listening key LK without causing the energization of relay ()DR, and connect her telephone set 0 to the cord circuit C which will enable her to converse with the subscriber at substation A, providing said subscriber at A has not replaced his receiver upon its switchhook. Thus, it is clear that the operator will only be able to connect her telephone set 0 to the cord circuit C when one or both of the subscribers at A and B has or have replaced the receiver upon its switchhook, but cannot connect said telephone set 0 to the cord (1 when both the calling and called subscribers have their receivers off their respective switchhooks.

Assuming now that the conversation has terminated, and the subscribers at A and B have replaced their receivers upon their respective switchhooks, supervisory relays AR and CR will restore to close circuits for the supervisory lamps AS and CL, respectively. the circuit for lamp AS being established from battery through the said lamp AS, alternate contact 60 of relay SR, to ground through normal contact 14 of relay AR, and the circuit for the lamp CL being from battery through the said lamp CL, normal contact of relay BUR, conductor 42 alternate contact 33 of relay SR to ground through normal contact 34 of relay CE. The supervisory lamps AS and (,lL will light over these circuits, and the operator observing them, will know that conversation has terminated and will withdraw the plugs AP and GP from the jacks J and J, respectively, whereupon the cord circuit C restores to normal, and the cut-off rela \'s CO and CO restore to normal.

lVhen the opera or of the cord circuit (1 removes the answering plug AP from the jack J of the calling line upon the termination of conversation the relay SR dccucrgizes and the opening of its alternate contact itlt) opens the locking circuit of the meter relay MR but as the relay MB is slow to release it is held momentarily energized after its locking circuit is opened. The closure of normal. contact of relay SR thus establishes an energizing circuit for the meter magnet MM traced from battery, through the winding of meter magnet MM, conductor 107, alternate contact 106 of the meter relay Ml, conductor 108 to ground at normal contact 100 of relay SE. The meter magnet MM is energized to operate the meter mechanism M to register an answered call from a calling common battery line at A. Meter relay MR and meter magnet MM also deenergize immediately thereatter.

It sometimes occurs that after the calling subscriber has stated his wants to the exchange operator, he replaces his receiver upon his switchhook and awaits a call from the operator when she has the called-tor subscriber on the line, and the operator may signal back the calling subscriber by operating a ringback key Till which will close its alternate contacts 11 and 12 to connect the ringing generator Rt} to the said calling subscribci"s line to signal the calling subscriber.

ieverting now to when the operator at cord C tested to determine the idle or busy condition of the called line ll, and assuming that said called for line is found busy, but that the operator disregards its busy condition and inserts the calling plug CP into the jack J and even though the listening key LK is in its operated position, the operator at cord circuit C will be prevented from listening in on the conversation at the called-for subscribefls line due to the fact that relay SR of cord C Will not energize since the low and high resistance windings of the relay SR of cord C will be shunted by the low resistance circuit of a sleeve relay SR of another cord circuit already connected to another jack which is in multiple circuit with the calling jack J, it the called-tor line is busy as a calling line, and in case the called-for line is busy as a called line, the low and high resistance windings of relay SR of cord circuit C will be shunted by the low resistance circuit of a sleeve relay SR of another cord circuit already connected to a jack of the called-for line which jack is in multiple circuit with the calling jack J. Relay SR failing to energize, relay RR will energize over a circuit traced from battery potential present on the ring contact of the jack J, which battery potential is provided from another cord circuit already connected to the called-"tor subscribers line, ring contact ot plug Cl, normal contact 48 of the relay IR, winding (i of ILJgfltiilg coil RC, through the winding of said relay RR, normal contact 62 of relay RCR, normal contact 50 of relay SR, winding 1) of the repeating coil RC, normal contact 49 of relay TR. tip contact of plug Cl and to the other side of battery at the tip contact of the calling jack J, which is in multiple circuit with the jack to which the other cord circuit is connected. Relay RR energizing closes its alternate contact 63, thereby closing a circuit for the operators disconnect relay ODR which will energize and open its normally closed contacts 18 and It) to prevent the operator from listening in on the conversation even though she does operate her listening key LK. The circuit for the said relay ODR may be traced from battery, through the winding of said relay ()DR, alternate contact 23 of the listening key LK, conductor 24, to ground through alternate contacts 63 of relay RR. Thus, it is clear that I have prov ded means for preventing an operator of a cord circuit from listening in on a busy called-for line. Should the operator ot the cord circuit attempt to operate the meter M by inserting an answering plug Al ot a cord circuit C in the jack .l ot a non-calling line to register it'alse answered connections she will be prevented from operating the meter M in the following manner. hen the answering plug Al is inserted into the jack .l of a min-calling line the relay SR of the cord circuit used and the cut otf relay C0 of the line circuit associated with the jack J are energized as before described. The relay SR upon energization closes its alternate conta'ts l0 and 13 but the relay All. does not energize as the circuit for the relay AB is not completed through the switchhook contacts of a calling common battery substation as A. As the relay AR remains deenergized its normal contact 14 remains closed and a ground to ground connection is closed through the meter relay MR traced from ground at normal contact 14. of the relay AR, conductors 101 and 102, normal conion tact 103 of relay MR, through the winding of relay MR, conductor 104 to ground at alternate contact 100 of relay SR. This ground to ground connection just traced shunts out the battery which is fed through the lamp AS to operate the relay MR when the answering plug AP is connected to the jack J of a calling common battery line and as the relay MR- remaina deenergized due to this ground to ground shunt just traced its alternate contact 106 remains open and when the operator again withdraws the plug from the jack J of the noncalling common battery line the relay SR deenergizes. The closing of normal contact 100 of relay SR does not affect the meter magnet MM as before described as the meter relay MR remains deenergized and as its alternate contact 106 remains open the meter magnet MM is not allected. Thus it is seen that the operator cannot cause the meter magnet MM to operate to register false calls as only such calls as have been established with a calling common battery subscriber are registered and then only after the answering plug AP has been dis connected from the jack of the calling line.

Referring again to the attempt of a second operator to answer a call from calling common battery subscriber subsequent to the first operator, the relay SR of the second cord fails to operate as previously described and as its alternate contacts 60 and 100 remain open no energizing circuit for the meter relay MB.- is closed and no reg stration of the meter takes place when a second operator attempts to answer a call after the first operator has seized the call.

Having described my cord circuit for in lerconnecting common battery subscribers telephone lines, I will now describe the operation of my cord circuit in interconnect- Eng magneto subscriber telephone lines.

Assuming that the subscriber at the magneto substation D initiates a call by operating the hand generator 57 at his substation D, the drop signal DS will operate to indicate to the operator at cord circuit C that her attention is desired, the circuit for the drop si nal DS being from one side of the generator 9 atsubsta-tion D, line limb 74, normal contact 75 of jack LJ, through the winding of said signal DS, normal con tact 76 of jack LJ, line limb 77, and to the other side of the generator 9 through the alternate contact 78 of said generator, which alternate contact 78 will be closed when the generator 9 is operating. The operator observing the operated signal DS will insert the answering plug AP of the cord G into the answering jack LJ which will open normal contacts 75 and 76, and at the same time automatically restore the signal DS to normal. and she will then throw her listening key LK to connect her telephone set to the cord C as described in the foregoing partof this specification. The sleeve relay SR will not energize when the plug AP is connected to the sleeve of said jack LJ, and since relay SR fails to energize, the supervisory relay AR will not energize at this time. The relay SR as just described does not operate when the cord circuit C is connected to a calling magneto line as D and therefore the meter relay MP. is not effected as alternate contacts 60 and 100 of relay SR remain open and no registration of answered calls are made when the calling line is a magneto line. The operator of cord C will now inquire the wants of the calling subscriber at substation D and assuming that the subscriber at substation E is wanted. the operator will insert the calling plug CP of cord G into the jack LJ of the called-for subscribers line E, whereupon the plug GP opens the normally closed contacts 7 5 and 76 of said jack LJ' to remove the signal BS from the control of calledfor subscriber E. The sleeve relay SR will not operate when the plug CP is inserted into the jack LJ, since the sleeve of said jack LJ is free from ground and as the relay SR fails to energize no circuit is established for the supervisory lamp signal CL and the said signal will not burn in this instance before the ringing key RK is operated, as was the case when the cord C was connected to a common battery telephone line. lhe operator will now operate one of the plungers of the ringing key RK to apply ringing current to the called for subscribers line, and assuming that the call bell at the called-for substation E is responsive to ringing current from the frequency generator G, the plunger of the ringing key RK corresponding to generator G will be operated, and when in its fully operated position, the alternate end spring contacts 39 and 44 of the ringing key R-K will be closed, thereby closing an energizing circuit for the ringing control relay RCR. The cir uit for the ringing control. relay RCR is from battery, through the winding of said relay BUR, conductor 35, normal contact 37 of relay SR. conductor 38, alternate contact 39 ot the end spring of key BK, to ground. through the normal contact 34 of relay CR. Relay RCR energizes over this circuit and closes its alternate contact 43, whereby a circuit is closed for the interrupter relay IR- traced from battery through the upper winding of said relay IR, alternate contact 43 of relay R-CR, alternate contact 44 of the end sprin" of the ringing key BK to ground. The relays RC3 and IR remained energized over the above traced circuits to apply ringing current to the called for subscribers line E, so long as the plunger of the ringing key RK is fully operated to close the alternate end spring contacts 39 and 44- of said ringing key RK, but when the operator removes her finger from the plunger, the same Will restore to open the said alternate contacts 39 and 44, thereby opening the circuits of the relays RCR and IE to cause the same to restore to prevent the further application of ringing current to the called-for subscribers line. The ringing control relay RCR is not provided with a locin the present connection, as was the case when the plug C? was connected to a jack of a common battery line, due to the fact that relay SR does not energize to close a loci:- ing circuit for said ringing control relay RCR. Since relay RUR- does not lock up, it is obvious that the interrupter relay IE will not operate intermittently to apply ringing current to the called-for line, and that it will be necessary to close the alternate end spring contacts 39 and 44 of the ringing key BK each time ringing current is applied to the called-for subscribers line, that is, each time ringing current is applied to the called-for subscribe-us line, the operator must operate the plunger of the ringing key PK to its fully operated position. The circuit for the ringing current may be traced from ground, through generator G, alternate contact 53 of ringing key BK. conductor 54, alternate contact 49 of relay IR, tip contacts of plug CP, and jack LJ, call bell and normal contact at substation E, ring contacts of jack LJ and plug GP, to ground through the alternate contact 48 of relay IR. When the end spring contacts 39 and 44 of the ringing key RK are opened the energizing circuits for relays IR and RCR are opened simultaneously but relay IR Will deenergize first and then relay RCR will deenergize, since it is slow-acting due to its construction, so that when ringing current ceases to be applied to the called subscrihci"s line, a circuit will be closed for the ringing current stored in the condenser associated with the call bell at the substation E and also for the line capacity traced from the ring contacts of jack LJ and plug C1 normal contacts 48 and 95 of relay IR, alternate contact 62 of relay RCR, normal contact 5-0 of relay SR, Where it is discharged into the repeating coil RC. This circuit just traced provides a discharging circuit for said stored ringing current to prevent the operation of relay RP when relay RCR restores. A revertive ringing tone is also transmitted to the calling subscriber at substation D to notify him that the called-for subscriber is being signaled, over a circuit traced from ground, through generator G alternate contact 56 of relay IR, winding 5 of the repeating coil RC, normal contact 50 of relay SR, alternate contact 62 of relay RC1 to ground through the alternate contact 95 of relay IR. The operator may leave her key LK operated lower windi 0t until she hears a response from the calledfor subscriber at substation E, whose response she will hear during a went period or when the ringing key BK and the relay IR are in their normal positions, whereupon she restores it to normal.

The talking circuit for the calling and called subscribers at substations D and 13] may be traced over the heavily marked conductors.

lVhcn converse ion has term nated and the subscrib have replaced their receivers upon their respective SWl'tCllllOOliS and ring off by operating their hand gi'znerators g and g, supervisory signal.) AS and CL will light to indicate to the operator that conversation has terminated. Assuming that the calling subscriber at substation D has replaced his receiver upon its switchhook and operates his hand generator g, relay RR will energize over a circuit traced from one side of the generator 9 at substation D, tip contacts of jack LJ and plug AP, normal contact 12 of ringback hey RB, winding a of repeating coil RC, normal contact 13 of relay SR, through the winding of said relay RR. winding 0 of RC, normal contact 11 of RB, ring contacts of plug Al? and jack LJ, an-ernate contact 78 to the other side of the generator g. Relay RR energizing over this circuit closes its alternate contacts 85, thereby closing a circuit for the supervisory relay AR traced from battery, through the -i relay AR, normal contact 10 of relay SR, normal contact 86 of listening key LK to ground through alternate contact 8-5 of relay RR, and relay AR energizing over this circuit closes a locking circuit for itself which may be traced over the previously traced circuit up to point 87 and then to ground throughv alternate contact 14 of said relay AR, aud a circuit is also closed for the supervisory signal AS, traced from battery, through the al AS, normal contact 60 of SR, normal contact relay RR (which rela RR will restore ween the hand generator 9 at substation D is no longer operated), alternate contact 14 of relay AR to ground. The lamp AS will be actuated by current lowing over this circuit to notify the operator at cord C that the calling subscriber has replaced his receiver, and that the connection is no longer desired.

The subscriber at substation E upon replacing his receiver upon its switchhoo-k will ring oil to cause the energization of relay RR traced from the hand generator 9 at substation E, tip contacts of jacl; LJ and plug GP, normal contact 49 of relay IR, winding Z) of the repeating coil RC, normal contact 50 or relay SR, normal contact (52 of relay RCR, through the winding of relay RR', winding d of RC, normal contact 48 of relay IR, ring contacts of plug CP and jack LJ', alternate contact 80 and to the other side of the hand generator g. Relay RR energizing over this circuit, closes an energizing circuit for the supervisory relay CR, traced from battery through the lower winding of said relay CR, normal contact 47 of relay SR, normal contact 90 of the listen ng key LK, conductor 91, to ground through alternate contact (33 of relay BR, and relay CR energizing over this circuit will close its alternate contact Ell and lock up to ground through the said alternate contact 34 of relay CR. Relay CR energizing also closes a circuit for the calling supervisory signal UL traced from battery through the signal CL, normal contact 3'2 of relay RCR, normal contact 33 of relay SR, normal contact 92 of relay RUB, normal contact 63 of relay RR (relay RR restoring when generator g ceases operating) to ground through alternate contact 34 of relay CR. The supervisory signal CL lights over this circuit to notify the operator that the subscriber at substation I) has rc placed his receiver upon its switchhook. The operator observing the two burning signals will operate her listening key LK to open its normally closed contacts 86 and 90 to open the circuits of supervisory relay AR and CR, respectively, to cause said relays to restore and open the circuits of the supervisory signals AS and CL, and will then restore said key and then withdraw the plugs AP and CP from their respective jacks LJ and LJ', whereupon the system is restored to its normal position.

Reverting back to when the subscriber at substation D replaced his receiver upon its switchhook and operated his hand generator 5 to cause relay RR to energize, relay AR energizing and remaining energized. and the supervisory signal AS burning after relay RR restores, now should the subscribeat substation D desire to initiate anothcncall or communicate with the operator at cord C, he may do so by operating his hand generator g, to again effect the cnergization of relay RR, which will remain energized so long the generator 1 is operated, and relay RR energizing will open its normally closed. contact 85, thereby opening the circuit of the supervisor signal AS to can-ac the efiacement of said signal AS. The operator observing the effacement of said signal AS, will know that the subscriber at sub station D has initiated another call, and will take care of it in the same manner as hereinbefore described. The subscriber at substation E may recall and signal the operator at cord C in the same manner, by operating his hand generator 9 to cause the energization of relay HR, to bring about the efi'acemcnt of the supervisory signal (L to indicate to the operator that the subscriber at substation E has initiated a call and she will take care of the call in the usual manner, pointed out in the foregoing specification.

The operation of my cord circuit C is the same as described above when used for interct'mnccting a common battery telephone line, and a magneto telephone line, that is, eilhrr end of the cord U will operate in the same manner when connected to a common baitcry telephone line described in the foregoing specification when connection is made with a common battery telephone line, and will operate in the same manner when connected to a magneto line, as set out above in describing its connection with a magneto telephone line.

From the foregoing specification, it will be clearly understood how the cord (l of my invention will operate when used for interconnecting a common battery telephone line, and a magneto telephone line, so that a description of the same is not deemed nece sary.

From the foregoing SPOClfiCilllOll, it will be clearly understood that the meter relay MR will only operate when the answering end of the cord C is connected to a common battery calling line and further that the meter magnet MM will operate when the connection is taken down after the termination of conversation. It is also clear that the meter M will only register such answered connections as are established with a calling common battery line and that it is impossible for the operator to register false answered connections by inserting an answerin plug AP of a cord G into the jack J ot a non-calling line.

Having described a particular embodiment and circuit arrangement of my invention, it is to be understood that I do not wish to be limited to the exact embodiment and circuit arrangement as described and shown, as many modifications and changes will readily suggest themselves to those skilled in the art, but I intend to cover all modifications and changes which may come within the spirit and scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters latcnt ot the United States is:

1. In a telephone system including tclephone line-i, a link circuit having an answering plug and a calling plug for interconnecting the same, a meter relay and a meter magnet asst 'iatcd with said link circuit, the anz-iwcring plug of said link circuit adapted to be coma-vied to a calling common battery telephone line to operate said meter relay to condition means for a subsequent operation of said meter magnet, said answering plug adapted to be disconnected from said telephone line upon the termination of the call to cause the operation of said meter magnet.

2. In a telephone system including telephone lines, a link circuit hav ng an answering plug and a calling plug tor interconnect-- ing the same. a meter relay and a meter mag not associated with said link circuit, the answering plug of said link circuit adapted to be connected to a common battery telephone line to operate said meter relay to condition means tor a subsequent operation ol said m ter magnet, said answering end of said link circuit adapted to be disconnected from said telephone line to cause said meter magnet to operate to register an an swered call.

3. In a telephone system including telephone lines, a link circuit for interconnect ing the same. a meter relay and a meter magnet associated with said link circuit, a sleeve relay. said link circuit adapted to be connected to a calling common battery subscribers line to operate said sleeve relay, a supervisory relay controllable by said sleeve relay and over said calling connnon battery line, said sleeve relay operating said meter relay to condition means for a subsequent operation of said meter magnet to register an answered call.

4. In a telephone systcm including telephone lines, a link circuit for interconnecting lines of dill'ercnt character, a meter relay and a mete n agnet associated with said link circuit, a sleeve relay, said link circuit adapttd to be connected to a calling common battery line to cause said sleeve relay to operate, a supervisory relay controlled by said sleeve relay and over said calling common battery line, said sleeve relay operating said meter relay after said supervisory relay operates, and a locking circuit for said meter relay, said meter relay conditioning means for a subsequent operation o'l said meter magnet, said link circuit adapted to be disconnected from said calling line to cause said lllClcl' magnet to operate to register an answered call.

5. In a telephone system including telephone lines, a link circuit for interconnecting lines of dillcrent character, a meter relay and a meter magnet associated with said link circuit, a sleeve relay, said link circuit; adapted to be connected to a calling common battery line to operate said sleeve relay, a supervisory relay controlled by said sleeve relay and over said calling line, said supervisory relay adapted to be energized to cause said meter relay to operate, a locking circuit for the said meter relay, and means controlled by said meter relay and said sleeve relay tor operating said meter magnet to register an answered call.

6. In a telephone system including telephone lines, a link circuit for intercoimect ing lines of different character, a slow acting meter relay and a meter magnet associated with said link circuit, a sleeve relay,

said link circuit adapted to be connected to a calling common battery line to cause said sleeve relay to operate, a :I- upcrvisory relay controlled by said sleeve relay and over said calling line, said supervisory relay adapted to be energized to cause said meter relay to operate and a locking circuit for the said meter relay, said slow acting meter relay conditioning switching means for a subse quent? operation of said meter magnet, said link circuit adapted to be disconnected from said calling common battery line to dccnergize said sleeve relay to permit said meter magnet to energize to register an answered call.

7. In a telephone system including telephone lines, a link circuit for interconnecting lines of ditterent character. a slow to release meter relay and a meter magnetassociated with said link circuit, a sleeve re lay, said link circuit adapted to be connected to a calling common battery line to operate said sleeve relay, a supervisory relay controlled by said sleeve relay and said calling line, said supervisory relay adapted to be operated to permit said meter relay to operate and a locking circuit for said meter relay, said slow to release meter relay conditioning switching means for a subsequent operation of said meter magnet, said link adapted to be disconnected from said calling common battery line to deencrgize said sleeve relay to permit said meter magnet to energize through switching means of said sleeve relay and said switching means of said slow to release meter relay to register an answered call.

8. In a telephone system including telephone lines, a link circuit for interconnecting lines of difi'erent character, a meter relay and a meter magnet associated with said link circuit, a sleeve relay, said link circuit, adapted to be connected to the jack of an idle or noncalting common battery line to cause said sleeve relay to operate, a supervisory relay associated with said link circuit, said sleeve and supervisory relays controlling the operation of said meter relay, said supervisory relay remaining inert when said link is connected to said jack of said idle or noncalling line, a shunt controlled by said supervisory relay to maintain said meter relay inert to prevent said meter relay energizing when said link circuit is connected to an idle or noncalling line.

9. In a telephone system including telephone lines, a link circuit for interconnecting lines of different character, a meter relay and a meter magnet associated with said link circuit, a sleeve relay for said link circuit, said link circuit adapted to be connected to a jack of an idle or non-calling common battery line to cause said sleeve relay to operate, a supervisory relay for said link circuit remaining inert when said link is connected to Ill) said idle or non-calling line, a shunt controlled by said supervisory relay to maintain said meter relay inert to prevent said meter relay energizing subsequent to the removal of said link from said jack.

10. In a telephone system including telephone lines of difi'erent character and a link circuit for interconnecting the same, a meter relay and a meter magnet associated with said link circuit, a sleeve relay for said link circuit, said link adapted to be connected to a jack of a busy or calling line or a jack of an idle or non-calling common battery line to cause said sleeve relay to operate, a supervisory relay for said link circuit controlled by said sleeve relay and over the connected calling common battery line, said supervisory relay remaining inert when said link is connected to an idle or noncalling line and energizing when said link circuit is connected to a calling line, a shunt controlled by said supervisory relay to maintain said meter relay inert to prevent said meter relay energizing subsequent to the removal of said link from the jack of an idle or noncalling line to prevent said meter magnet energizing to register a false answered call.

11. A telephone system including telephone lines, a link circuit having an answering plug and a calling plug for interconnecting the same, a meter relay and a meter magnet associated with said link circuit, a sleeve relay, said link circuit adapted to be connected to a calling telephone line to 'ause said sleeve relay to operate, a supervisory relay controlled by said sleeve relay and over said calling line, said supervisory relay adapted to be energized to cause said meter relay to operate to condition means for the subsequent operation of said meter magnet, said link circuit adapted to be disconnected from said telephone line to permit said meter magnet to energize to register an answered call.

12. In a telephone system including telephone lines terminating at different operators positions at a central exchange. link cir cuits for interconnecting said telephone lines, a meter relay and a meter magnet, a sleeve relay in each of said link circuits, said link circuits adapted to be connected to a calling telephone line to cause said sleeve relay to operate to condition means including said meter relay to cause the subsequent operation of said meter magnet, said link circuit adapted to be disconnected from said telephone line to cause said sleeve relay to deenergize to cause said meter magnet to operate to register an answered call, a second link circuit adapted to be connected to the same falling telephone line, the sleeve relay in said second link circuit remaining inert when said second link circuit is connected to said telephone line subsequent to the connection ot' the first link circuit to the same calling telephone line whereby the meter magnet in the second link circuit is prevented from operating upon the disconnection of the second link circuit from the telephone line to falsely register an answered call.

13. In a telephone system including telephone lines, terminating at a central exchange at different operators positions, link circuits for interconnecting said telephone lines, a sleeve relay in each of said link circuits, one of said link circuits adapted to be connected to a calling common battery telephone line to cause said sleeve relay to operate, a supervisory relay controlled by said sleeve relay and over said calling line, an operators set, a listening key adapted to connect said set to said link circuit, a meter relay and a meter magnet, said supervisory relay adapted to energize to cause the operation of said meter relay to condition means for the subsequent operation of said meter magnet to register an answered call, a second link circuit adapted to be connected to said calling common battery telephone line, an operators disconnect relay, means in said second link circuit adapted to cause the energization of said operators disconnect relay to prevent the connection of the second operators set to the said link circuit.

Ll. In a telephone system including a calling line and a called line, a link circuit for interconnecting said lines, a sleeve relay, a meter relay and a meter magnet, said link circuit adapted to be connected to said calling line to cause said sleeve relay to operate, a supervisory relay controlled by said sleeve relay and over said calling line, an operators set, a listening key adapted to connect said operators set to said link circuit, a second supervisory relay controlled over said called line, an operators disconnect relay, said first supervisory relay adapted to be energized to cause the energization of said meter relay to condition means for the subsequent opera tion of said meter magnet, said operators disconnect relay adapted to be energized through the contacts of said supervisory relays when said listening key is operated subsequently to the energization of said second supervisory relay, said link circuit adapted to be disconnected from said calling line to cause the said meter magnet to energize to register an answered call.

15. In a telephone system including tele phone lines, a link circuit having an answering plug and a calling plug for interconnecting said telephone lines, an operators set, a listening key for connecting said operators set to said link circuit, an ol')eratoi"s disconnect relay adapted to render said listening key ineffective to connect said operato rs set to said link circuit, said calling plug adapted to be connected to a busy line to cause means in said link circuit to operate to permit the energization of the operators disconnect relay to render said listening key ineffective to connect said operators set to said link circuit whereby said operators set is prevented from connecting with said link circuit.

16. In a telephone system including tele phone lines, a link circuit having an answering plug and a calling plug for interconnecting said telephone lines, an operators set. a listening key for connecting said operators set to said link circuit, an operators disconnect relay adapted to render said listening key ineffective to connect said operators set to said link circuit, said calling plug adapted to be connected to a busy line to cause means in said link circuit to operate to permit the energization of the operators disconnect relay to render said listening key ineffective to connect said operators set to said link circuit whereby said operators set is prevented from connecting with said link circuit, said calling plug adapted to be connected to an idle line, said means in said link circuit remaining inoperative and said operators disconnect relay remaining inoperative to permit the said operators set to be connected to said link circuit.

In testimony whereof I have signed this specification.

BERT A. VVALLACE. 

